ELECTROKINETICS OF CHOLESTEROL IN THE PRESENCE OF BILE-SALT AND BILE-SALT LECITHIN MIXTURES

The effects of bile salts and bile salt + lecithin mixtures on the electrokinetic potential (ζ) of cholesterol are discussed in this paper. By comparison of the variation of ζ with pH, without the addition of any bile salt, two different mechanisms are proposed to describe the adsorption of sodium cholate and deoxycholate on the cholesterol surface at three different pH values. The important affinity of deoxycholate ions for the cholesterol surface is demonstrated, mainly when the pH is far from the isoelectric point of the cholesterol. Both salts, however, can change the sign of the surface charge of cholesterol from positive to negative at low pH. The effect of pH on ζ for four different sodium deoxycholate + lecithin mixtures is also considered, and the possibility of lecithin adsorption on the cholesterol surface is discussed. © 1990.